A transistor of the trench gate structure includes a gate electrode extending in the depth direction of the semiconductor region. In the transistor of the trench gate structure, the device area can be made smaller than in the transistor of the planar gate structure. For instance, in a MOS (metal oxide semiconductor) transistor of the trench gate structure, a source region, a base region, and a drift region are provided in a pillar-shaped semiconductor section adjacent to the trench gate structure. Furthermore, in the semiconductor section, a high concentration region having high impurity concentration is provided together with the source region.
In such a semiconductor device, with the miniaturization of the pillar-shaped semiconductor section, the positional accuracy of the high concentration region provided in the semiconductor section becomes important. That is, if the high concentration region is misaligned, impurity contained in the high concentration region affects the base region and causes variation in characteristics. In semiconductor devices, it is important to achieve stable characteristics.